Species relationships between antifungal chitinase and nuclear rDNA (internal transcribed spacer) sequences in the genus Hordeum.

The sequences of the chitinase gene (Chi-26) and the internal transcribed spacer of 18S - 5.8S - 26S rDNA (ITS1) were determined to analyze the phylogenetic relationships among species representing the four basic genomes of the genus Hordeum. Grouping analysis based on data for Chi-26 gene sequences placed Hordeum secalinum (H genome) near the Hordeum murinum complex (Xu genome), and Hordeum bulbosum distant from the other species that carried the I genome. ITS sequence data showed the expected grouping based on the genome classification of the species studied. Different sequences of ITS were detected even in the genomes of the diploid species. The results are interpreted in terms of defective or unfinished concerted evolution processes in each taxon.     

Speciation and Species Separation in Hordeum L. (Poaceae) Resolved by Discontinuous Molecular Markers1

Abstract: Amplified fragment length polymorphisms (AFLPs) were used to evaluate the capacity of discontinuous markers to reveal genetic structure within Hordeum , a challenging higher plant genus from the standpoint of natural systematics. Phylogenies of 63 accessions encompassing nine species from four Hordeum sections were inferred from polymorphisms scored at 600 loci. Phylogenies based on sequences from the nuclear internal transcribed spacer (ITS) region were constructed for comparison, but revealed severe sampling errors inherent to single genes. Although superior by virtue of providing genome-wide estimates of genetic similarity, the adoption of AFLPs in infrageneric studies requires caution. Comigrating AFLP bands studied here could be divided on the basis of band intensity variation into two types that are □ 100 % identical and < 40 % identical in DNA sequence, respectively, in infrageneric comparisons. Thus, the careful selection of AFLP bands to be analyzed bears heavily upon their phylogenetic utility. Within the H. murinum complex, which encompasses three morphologically distinct subspecies, AFLP data from 37 accessions reveal unexpected genetic differentiation between H. murinum, glaucum populations to the east and west of Alexandria (Egypt), suggesting the presence of allopatric speciation in the wake of human settlement.     

Phylogenetic analysis in the Festuca-Lolium complex using molecular markers and ITS rDNA

 Molecular markers were used to investigate phylogenetic relationships among the eight species of ryegrass (Lolium) and 11 species of fescue (Festuca). RAPD and RFLP analyses were carried out on total bulked DNA from each population. Factorial analysis of a phenetic distance matrix yielded three major groups: (1) fine-leaved fescues, (2) broad-leaved fescues and (3) ryegrasses. Six non-coding regions of chloroplastic DNA were PCR-amplified, then digested by 20 restriction enzymes. Nuclear rDNA sequences, including internal transcribed spacers (ITSs) were used to estimate the average proportion of nucleotide substitutions. The correlation between substitution rate estimated from ITS sequences and that estimated from organelle DNA restriction sites was very high (0.94), and the corresponding UPGMA trees were very similar, with a slightly better resolution of the ITS tree in the Lolium genus. The time-scale inferred from substitution rates indicated that the period since divergence of the broad-leaved fescues from the fine-leaved fescues was four times as long as that since divergence of the genus Lolium from the former. Among the broad-leaved fescues, meadow fescue was closer to the Lolium group, while F. glaucescens and tall fescue were very closely related. North-African fescues were clustered together and giant fescue was the most differentiated species in this group. Our dataset was merged with ITS sequences recovered from the EMBL database, and the neighbor-joining method was used to draw a phylogenetic tree. In this tree, the tribe Poeae was clearly monophyletic, and more closely related to the Aveneae than to the Triticeae or Bromoideae. The genus Festuca appeared somewhat artificial, since Vulpia myuros and Dactylis glomerata were placed between fine-leaved and broad-leaved fescues. Received: 10 January 1997/Accepted: 21 February 1997     

Tilletia vankyi, a new species of reticulate-spored bunt fungus with non-conjugating basidiospores infecting species of Festuca and Lolium

A bunt fungus, exhibiting a spore germination pattern unique to known reticulate-spored species of Tilletia was found infecting plants in seed production fields of Festuca rubra ssp. rubra (red fescue) and F. rubra ssp. fallax (Chewing's fescue) in Oregon, and in seed lots of Lolium perenne (perennial ryegrass) from Australia and Germany. Teliospores germinated to form 20–40 uninucleate, non-conjugating basidiospores, and colonies derived from single basidiospores produced teliospores in culture. In inoculation studies using single basidiospore colonies, perennial ryegrass and L. perenne ssp. multiflorum (Italian or annual ryegrass) were infected. A phylogenetic analysis, based on ITS region rDNA, eukaryotic translation elongation factor 1 alpha, and the second largest subunit of RNA polymerase II demonstrated that the fescue and ryegrass bunts are conspecific, and distinct from known species of Tilletia.     

Comparative and evolutionary analysis in natural diploid and tetraploid weather loach Misgurnus anguillicaudatus based on cytochrome b sequence data in central China

To obtain the phylogenetic relationship between diploid and tetraploid Misgurnus anguillicaudatus, the mitochondrial cyt b gene in the diploid and tetraploid weather loach were isolated and sequenced. The DNA sequences were analyzed using MEGA 3.0 software to determine the phylogenetic relationship. Forty-five variable sites among cyt b gene sequences and 18 amino acid substitutions occurred within the diploid and tetraploid loaches as deduced from the nucleotide sequences analysis of the cyt b gene. The nucleotide pairwise distance between diploid and tetraploid loach ranged from 0.001 to 0.025. Phylogenetic analysis revealed evolutionary relationships between diploid and tetraploid loach. Our results indicated a significant difference between diploid and tetraploid loach about the cyt b gene. AMOVA analysis indicated that there were no significant genetic variations within diploid loaches (Fst = 0.2529, P > 0.05) and within tetraploid loaches (Fst = 0.0564, P > 0.05), neither. However, significant genetic differences were found between diploid and tetraploid loaches (Fst = 0.7634, P < 0.05). Thus, it is concluded that no reproductive isolation was found within the same cytotypes of different localities, but there was reproductive isolation between these two cytotypes. The diploid loach existed before the tetraploid loach in nature. The present study is the first to describe the phylogenetic relationships of natural polyploidy weather loach using mtDNA cyt b gene.     

Diversity and evolution of the Hordeum murinum polyploid complex in Algeria

Population diversity and evolutionary relationships in the Hordeum murinum L. polyploid complex were explored in contrasted bioclimatic conditions from Algeria. A multidisciplinary approach based on morphological, cytogenetic, and molecular data was conducted on a large population sampling. Distribution of diploids (subsp. glaucum) and tetraploids (subsp. leporinum) revealed a strong correlation with a North-South aridity gradient. Most cytotypes exhibit regular meiosis with variable irregularities in some tetraploid populations. Morphological analyses indicate no differentiation among taxa but high variability correlated with bioclimatic parameters. Two and three different nuclear sequences (gene coding for an unspliced genomic protein kinase domain) were isolated in tetraploid and hexaploid cytotypes, respectively, among which one was identical with that found in the diploid subsp. glaucum. The tetraploids (subsp. leporinum and subsp. murinum) do not exhibit additivity for 5S and 45S rDNA loci comparative with the number observed in the related diploid (subsp. glaucum). The subgenomes in the tetraploid taxa could not be differentiated using genomic in situ hybridization (GISH). Results support an allotetraploid origin for subsp. leporinum and subsp. murinum that derives from the diploid subsp. glaucum and another unidentified diploid parent. The hexaploid (subsp. leporinum) has an allohexaploid origin involving the two genomes present in the allotetraploids and another unidentified third diploid progenitor.     

Flowering Behaviour of Four Annual Grass Species in Relation to Temperature and Photoperiod

Populations of four co-habiting annual grass species Bromusmollis L. (Soft brome), Hordeum hystrix Roth (Mediterraneanbarley grass), Lolium rigidum Gaud. (Wimmera ryegrass) and Vulpiabromoides (L.) S. F. Gray (Squirrel-tail fescue) were examinedfor the presence and comparative levels of vernalization andphotoperiod response. This was evaluated as the number of daysfrom sowing to heading in both long (16 h) and short (normal,over-winter) photoperiods at two levels of temperature. Wide variation among the species in both vernalization and photoperiodicresponse was detected. L. rigidum possessed a high level ofvernalization response and was comparatively sensitive to photoperiodwhile V. bromoides possessed little or no vernalization responseand was comparatively insensitive to photoperiod. B. mollisand H. hystrix appeared to be intermediate between these twospecies for both responses. There were wide differences in timeto heading under long photoperiod (16 h) and high temperature(20 °C) of plants derived from seed of three of the speciesripened under non-vernalizing temperatures. This variation indicatesthe likely existence of genetic differences in vernalizationresponse between plants of these populations. The implications of these findings to the adaptability of thesespecies to the Australian environment have been outlined. Bromus mollis L., soft brome, Hordeum hystrix Roth, Mediterranean barley grass, Lolium rigidum Gaud, Wimmera ryegrass, Vulpia bromoides (L.) S. F. Gray, Squirrel-tail fescue, flowering, vernalization, photoperiod, temperature     

Genetic diversity in Mediterranean diploid and tetraploid Bromus L. (section Bromus Sm.) populations.

The levels of genetic diversity assessed from allozyme data were investigated in 25 populations of Mediterranean Bromus intermedius, B. squarrosus, B. lanceolatus, and B. hordeaceus from Algeria. The geographically restricted diploids B. intermedius and B. squarrosus displayed less genetic diversity (the mean population gene diversity of Nei (Hu) ranged from 0.03 to 0.12) than the widespread tetraploid colonizers B. lanceolatus and B. hordeaceus (Hu = 0.07-0.27). Deviations from Hardy-Weinberg expectations in diploid populations of B. intermedius and B. squarrosus were observed owing to heterozygote excess at several loci and suggested that these self-fertilizing species may have substantial amounts of allogamy. Tetraploid populations of B. lanceolatus and B. hordeaceus were largely homozygous at homologous loci and frequently exhibited intergenomic fixed heterozygosity in accordance with their alloploid origin. Genetic variation at the infraspecific level was mostly distributed within populations in the four species, B. hordeaceus showing the lowest level of interpopulation differentiation (Gst = 0.06) and the highest level of gene flow (Nm = 3.75). Consistent gene flows are in agreement with the strongest intercontinental invasive behaviour of B. hordeaceus. Less differentiation was reported in the literature among later introduced B. hordeaceus populations from England and Australia, indicating reduced differentiation under the process of colonization. Moderate divergence occured among the four taxa, with interspecific genetic identities ranging from 0.87 to 0.93. In spite of substantial genetic similarity, species were clearly differentiated, with each tetraploid being more closely related to a diploid: B. hordeaceus to B. squarrosus and B. lanceolatus to B. intermedius.     

Multilocus phylogenetic analyses within Blumeria graminis, a powdery mildew fungus of cereals

Blumeria graminis, a powdery mildew fungus, is an important plant pathogen that causes serious damage to a variety of cereal crops. In spite of the importance of the pathogen, information on phylogenetic structure within B. graminis is scarce. In this study we conducted phylogenetic analyses of B. graminis based on the DNA sequences of four different DNA regions (ITS, 28S rDNA, chitin synthase 1, and beta-tubulin). The analyses revealed that the protein-coding regions have higher amounts of phylogenetic signals than rDNA regions and are useful for phylogenetic analyses of B. graminis. The present phylogenetic analyses revealed nine distinct groups in the B. graminis isolates used in this study, a result which was commonly supported by all trees constructed from the four DNA regions. Isolates from a single host genus belonged to a single group except for isolates from Lolium and Bromus, in which the isolates were split into two and three groups, respectively. Isolates from Agropyron, Secale and Triticum formed a distinct clade (Triticum clade) with identical or similar DNA sequences. The Hordeum clade was a sister of the Triticum clade, and Poa and Avena clades were distantly related to the Triticum and Hordeum clades. This phylogenetic relationship of B. graminis is well concordant with the level of reproductive isolation between formae speciales and also with phylogeny inferred from a cytological study. Shimodaira-Hasegawa and Templeton tests using sequences of four different DNA regions significantly rejected the tree topology of plants. Therefore, possibility of co-speciation between B. graminis and its host plants was obscure in this study.     

Phylogenetic analysis in some Hordeum species (Triticeae; Poaceae) based on two single-copy nuclear genes encoding acetyl-CoA carboxylase

We investigate the phylogenetic relationship, and evolutionary history of 18 diploid and polyploid Hordeum species including 22 taxa based on two single-copy nuclear ACC1 and ACC2 genes using maximum parsimony, maximum likelihood, and Bayesian inference. The results of molecular phylogenetic analysis demonstrated genetic relationships among taxa and origin of polyploids. Our phylogenetic analyses revealed a clear alloploid origin of Hordeum capense, with Eurasian Hordeum marinum subsp. gussoneanum as the Xa genome donor and diploid Asian Hordeum roshevitzii as the H genome donor. The formation of hexaploid Hordeum lechleri likely involves hybridization between tetraploid Hordeum brachyantherum subsp. brachyantherum and a diploid possessing the I genome. The Acc1 and Acc2 gene data analyses suggested that Siberian Hordeum bogdanii might have be the common ancestor of the diploid New World Hordeum species. Perennial diploid South American species, Hordeum comosum was the first-diverging group within the clade of diploid American species in the analyses.     

Molecular phylogenetics of Hippophae L. (Elaeagnaceae) based on the internal transcribed spacer (ITS) sequences of nrDNA

 The genus Hippophae comprises 7 species and 8 subspecies according to the latest classification, and has shown enormous ecological, nutrient and medicinal values. Here we analyzed the phylogenetic relationships among 15 taxa of the genus by comparing sequences of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA (nrDNA). ITS sequences in Hippophae varied in length from 651 bp to 666 bp. The aligned sequences were 690 bp in length and 269 (39.0%) were variable sites with 150 being parsimony-informative. The amount of polymorphism observed within a taxon was extremely low in most taxa except for two putative hybrid species. The aligned sequences were analyzed by maximum parsimony (MP) and neighbor-joining (NJ) methods. In the strict consensus trees of parsimony analysis, the monophyly of Hippophae was supported by 100% bootstrap value. H. tibetana was at the basal position of the genus, and the remaining taxa formed two clades with high bootstrap support. The first clade included subspecies of H.␣rhamnoides and the other one consisted of remaining species. Parsimony analysis also suggested that the species H. tibetana, H. neurocarpa and H.␣salicifolia were all distinct. Although the sequence divergence among subspecies of H. rhamnoides was also remarkably high, the molecular data supported the monophyly of H. rhamnoides when H. rhamnoides subsp. gyantsensis Rousi was excxluded. The NJ trees showed essentially the same topology. The taxonomical arrangement that divided the genus into two sections was not supported based on the ITS sequences. However, the hybrid origin of H. goniocarpa and H. litangensis proposed previously was supported by the present ITS data. Received January 7, 2002; accepted May 10, 2002 Published online: November 22, 2002 Addresses of the authors: Kun Sun, Xuelin Chen, Ruijun Ma, Qin Wang, Institute of Botany, Northwest Normal University, Lanzhou 730070, China. Changbao Li, Song Ge (e-mail: gesong@ns.ibcas.ac.cn or song_ge@hotmail.com), Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.     

Gluconobacter sphaericus (Ameyama 1975) comb. nov., a brown pigment-producing acetic acid bacterium in the Alphaproteobacteria

Strain NBRC 12467(T )was examined genetically, phylogenetically, phenotypically, and chemotaxonomically. The DNA G+C content of the strain was 59.5 mol%. The strain represented low levels of DNA-DNA hybridization of 49-9% to the type strains of eight Gluconobacter species. The strain formed a cluster along with the type strains of G. albidus and G. kondonii in phylogenetic trees based on 16S rRNA gene sequences. In a phylogenetic tree based on 16S-23S rRNA gene ITS sequences, however, the strain formed an independent cluster from the type strains of the eight Gluconobacter species. Such phylogenetic relationships were supported by the calculated pair-wise 16S rRNA gene and 16S-23S rRNA gene ITS sequence similarities. The strain was distinguished from the type strains of the eight Gluconobacter species by 16S-23S rRNA gene ITS restriction analysis using five restriction endonucleases. The strain produced a water-soluble brown pigment and 2,5-diketo-D-gluconate from D-glucose, differing from the type strains of the eight Gluconobacter species, and acid from meso-erythritol very weakly, differing from the type strains of the remaining seven Gluconobacter species except for the type strain of G. roseus, but not from maltose, differing from the type strain of G. oxydans, and had Q-10. For the strain, which was once classified as G. oxydans subsp. sphaericus, Gluconobacter sphaericus (Ameyama 1975) comb. nov. is proposed. The type strain is NBRC 12467(T), which is also deposited as BCC 14448(T).     

Evolution of ITS1 rDNA in the Digenea (Platyhelminthes: Trematoda): 3′ End Sequence Conservation and Its Phylogenetic Utility

A comparison of ribosomal internal transcribed spacer 1 (ITS1) elements of digenetic trematodes (Platyhelminthes) including unidentified digeneans isolated from Cyathura carinata (Crustacea: Isopoda) revealed DNA sequence similarities at more than half of the spacer at its 3′ end. Primary sequence similarity was shown to be associated with secondary structure conservation, which suggested that similarity is due to identity by descent and not chance. Using an analysis of apomorphies, the sequence data were shown to produce a distinct phylogenetic signal. This was confirmed by the consistency of results of different tree reconstruction methods such as distance approaches, maximum parsimony, and maximum likelihood. Morphological evidence additionally supported the phylogenetic tree based on ITS1 data and the inferred phylogenetic position of the unidentified digeneans of C. carinata met the expectations from known trematode life-cycle patterns. Although ribosomal ITS1 elements are generally believed to be too variable for phylogenetic analysis above the species or genus level, the overall consistency of the results of this study strongly suggests that this is not the case in digenetic trematodes. Here, 3′ end ITS1 sequence data seem to provide a valuable tool for elucidating phylogenetic relationships of a broad range of phylogenetically distinct taxa. Received: 20 October 1997 / Accepted: 24 March 1998     

Hordein polymorphism in diploid and tetraploid Mediterranean populations of the Hordeum murinum L. complex

Polymorphism analyses of the hordeins, main storage proteins in barley, were conducted on 35 natural populations of Hordeum murinum s.l. from North Africa; this specific complex includes three subspecies with two ploidy levels: H. murinum subsp. glaucum (2n=2x=14), H. murinum subsp. leporinum and subsp. murinum (2n=4x=28). Twenty of these populations belong to the diploid subsp. glaucum, 14 other tetraploid populations belong to the subsp. leporinum. In addition, six populations of the tetraploid murinum were sampled in France: two along the Mediterranean coast and four in Brittany. The polymorphism observed in the electrophoretic patterns highlights strong correlations between bioclimatic features and di- and tetraploid taxa distribution. Moreover, the variation was not randomly distributed within the different ploidy levels, and is correlated with environmental factors. The ecological differentiation of the two main taxa, H. murinum subsp. leporinum and subsp. glaucum is clearly highlighted.     

Molecular phylogeny of the genus Hordeum using three chloroplast DNA sequences.

The genus Hordeum consists of three cytotypes (2x, 4x, and 6x). Its reproductive isolation has been incomplete between closely related species and hence the genetic relationship is reticulate and complex. We used 32 taxa of Hordeum and three chloroplast DNA sequences, matK, atpB-rbcL, and trnL-trnF in the current study. Molecular phylogenetic analysis based on sequence data of the three chloroplast DNA regions clearly demonstrated genetic relationships among taxa and origin of polypoids. The formation of H. secalinum likely involved hybridization between Hordeum marinum subsp. marinum and a Eurasian diploid possessing the H genome. The formation of hexaploid Hordeum brachyantherum involved hybridization between tetraploid H. brachyantherum and diploid H. marinum subsp. gussoneanum. The formation of three tetraploids, H. brachyantherum, Hordeum jubatum, and Hordeum guatemalense, probably involved hybridization between H. brachyantherum subsp. californicum and an altered H genome diploid. The formation of Hordeum arizonicum involved the two taxa Hordeum pusillum and H. jubatum.     

Production of transgenic tall fescue and red fescue plants by particle bombardment of mature seed-derived highly regenerative tissues

 Highly regenerative tissues of tall fescue and red fescue produced from mature seed-derived embryogenic callus were induced and proliferated on medium containing 2,4-dichlorophenoxyacetic acid (4.5 or 9.0 μM), 6-benzylaminopurine (0, 0.044, 0.44 or 2.2 μM) and cupric sulfate (0.1 or 5.0 μM) under dim-light conditions (10 to 30 μE m^–2 s^–1, 16 h light). Tall fescue tissues were transformed with three plasmids containing the genes for hygromycin phosphotransferase (hpt), phosphinothricin acetyltransferase (bar) and β-glucuronidase (uidA;gus), and red fescue with three plasmids containing hpt, uidA and a synthetic green fluorescent protein gene [sgfp(S65T)]. DNA from T₀ plants of eight independently transformed lines from tall fescue and 11 from red fescue were analyzed by PCR and DNA blot hybridization. The co-expression frequency of all three transgenes [hpt/bar/uidA or hpt/uidA/sgfp(S65T)] in transgenic tall fescue and red fescue plants was 25–27%; for two transgenes [hpt/bar or hpt/uidA for tall fescue and hpt/uidA or hpt/sgfp(S65T) for red fescue], the co-expression frequency was 50–75%. Received: 28 September 1999 / Revision received: 13 March 2000 / Accepted: 16 March 2000     

Bensingtonia pseudonaganoensis sp. nov., a novel ballistoconidium-forming yeast species isolated from plant leaves

Among the basidiomycetous yeasts isolated from plant leaves collected in different regions of China, two ballistoconidium-forming strains were revealed to represent an undescribed species of the genus Bensingtonia by conventional, chemotaxonomic and molecular phylogenetic characterization. Sequence analysis of the 26S rDNA D1/D2 domains and the internal transcribed spacer (ITS) region indicated that the novel species was located in the Agaricostilbum lineage and closely related to Bensingtonia naganoensis and Bensingtonia ciliata, with the former as its closest relative. The name Bensingtonia pseudonaganoensis sp. nov. is proposed (type strain: AS 2.2601^T = CBS 10121^T)     

Taxonomic re-assessment of <Emphasis Type="Italic">Phaseolus dasycarpus</Emphasis> (Leguminosae): Systematic position,chromosome studies and re-description

Based on new information on floral structures, seedling, fruit, seed, root, and leaflet characters, Phaseolus dasycarpus is re-described and illustrated. Its chromosome number was determined as 2n  = 22, with metacentric and submetacentric chromosomes, and karyotype formula of 9m + 2sm. Previous phylogenetic analyses of ITS and trnK sequence data, and those obtained in the present study, show P. dasycarpus to be aligned within section Pedicellati.

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Resumen  Con nueva información de estructuras florales, plántulas, frutos, semillas, raíz y folíolos, se redescribe e ilustra a Phaseolus dasycarpus. Se determina el número cromosómico 2n  = 22, con cromosomas metacéntricos y submetacéntricos y fórmula cariotípica = 9m + 2sm. Análisis filogenéticos previos con secuencias de ITS y trnK y los resultados obtenidos en el presente estudio, establecen a P. dasycarpus en la sección Pedicellati.

     

Intraspecific and within-isolate sequence variation in the ITS rRNA gene region of Pythium mercuriale sp. nov. (Pythiaceae)

Sixteen Pythium isolates from diverse hosts and locations, which showed similarities in their morphology and sequences of the internal transcribed spacer (ITS) region of their rRNA gene, were investigated. As opposed to the generally accepted view, within single isolates ITS sequence variations were consistently found mostly as part of a tract of identical bases (A-T) within ITS1, and of GT or GTTT repeats within the ITS2 sequence. Thirty-one different ITS sequences obtained from 39 cloned ITS products from the 16 isolates showed high sequence and length polymorphisms within and between isolates. However, in a phylogenetic analysis, they formed a cluster distinct from those of other Pythium species. Additional sequencing of two nuclear genes (elongation factor 1 alpha and beta-tubulin) and one mitochondrial gene (nadh1) revealed high levels of heterozygosity as well as polymorphism within and between isolates, with some isolates possessing two or more alleles for each of the nuclear genes. In contrast to the observed variation in the ITS and other gene areas, all isolates were phenotypically similar. Pythium mercuriale sp. nov. (Pythiaceae) is characterized by forming thin-walled chlamydospores, subglobose to obovoid, papillate sporangia proliferating internally and smooth-walled oogonia surrounded by multiple antheridia. Maximum likelihood phylogenetic analyses based on both ITS and beta-tubulin sequence data place P. mercuriale in a clade between Pythium and Phytophthora.     

Genetic variation in three species of Hordeum,and the selection of accessions for the Barley Core Collection

Starch gel electrophoresis of isozymes was used to investigate the level and distribution of genetic variation in accessions of three wild, diploid Hordeum species. Allelic variation was assessed for seven isozyme loci and used in the statistical analysis of 18 accessions of Hordeum brachyantherum subsp. californicum, 29 accessions of H. murinum subsp. glaucum and 11 accessions of H. pusillum. A major purpose with this study was to evaluate the selection of accessions for the international Barley Core Collection, complementing existing passport data. Allelic variation was found in all three species. The variation was mainly between accessions, as most accessions were fixed for certain alleles. Since all three species are self-pollinated, this was anticipated. The fact that the accessions have undergone one or several regeneration cycles from a rather limited number of individuals, after being collected, likely also have reduced the variation. The accessions were clustered by subjecting the genetic distances between them to UPGMA statistical treatment. The clusters in the dendrograms displayed for H. brachyantherum subsp. californicum and H. pusillum distinct patterns related to the geographical origin of the accessions. The accessions of H. murinum subsp. glaucum were less variable than the other two, and did not reveal such a clear pattern. By comparing the already made, geographically based, selection of accessions with the results from this study, it was evident that the selection had worked fairly well for H. brachyantherum subsp. californicum, but less so for the other two species.